1. Field of the Invention
The present invention relates to an atmosphere replacement apparatus capable of replacing an atmosphere around a substrate during transportation, a substrate transport apparatus, a substrate transport system, and an Equipment Front End Module (EFEM).
2. Description of the Related Art
Conventionally, production of semiconductors has been carried out by various processing steps performed on a wafer as a substrate. In recent years, circuit miniaturization and high integration of elements have been increasingly promoted. It has been required to maintain a high level of cleanliness around a wafer to prevent adhesion of water and particles to a surface of a wafer. Further, to prevent changes in properties of a surface of a wafer, such as oxidization, it has been performed to make a periphery of a wafer vacuum or nitrogen atmosphere that is an inert gas.
In order to properly maintain such an atmosphere around a wafer, a wafer is managed by placing in a sealable storage pod called a Front-Opening Unified Pod (FOUP), and nitrogen is filled inside the pod. Further, to transfer a wafer between a FOUP and a processing apparatus for processing a wafer, an Equipment Front End Module (EFEM) as disclosed in Patent Application Publication No. 2012-49382 is provided. An EFEM constitutes a wafer transport chamber that is substantially closed inside a housing, comprises a load port that functions as an interface unit between the FOUP on one of opposite wall surfaces, and is connected to a load lock chamber that is a part of a processing apparatus on the other of the wall surfaces. In a wafer transport chamber, a wafer transport apparatus is provided, constituting a wafer transport system for transporting a wafer. By using a wafer transport apparatus, a wafer is loaded and unloaded between a load lock chamber and a FOUP connected to a load port.
In other words, a wafer is taken out from the FOUP (a load port) that is one transfer position by using the wafer transport apparatus, and transported to the load lock chamber that is the other transfer position. The processing apparatus performs processing for a wafer transported through the load lock chamber within a processing unit called a process chamber. After the processing is completed, the wafer is taken out through the load lock chamber, and returned to the FOUP.
The interior of the processing apparatus is made to a special atmosphere, a vacuum or the like in accordance with the processing, to enable quickly the processing for a wafer. The interior of the wafer transport chamber in the EFEM is kept in a clean air atmosphere at a high level of cleanliness by introducing the air cleaned through a chemical filter or the like, to prevent contamination due to adhesion of particles or the like to the surface of a wafer during transport.
However, in recent years, as the cleanliness has been advanced more and more, although the cleanliness is high in the wafer transport chamber of EFEM, the influence of the air atmosphere different from the interior of the FOUP or the processing apparatus has been concerned.
In other words, the air atmosphere has a possibility of adhesion of moisture and oxygen to the surface of a substrate, causing corrosion and oxidation. Further, when a corrosive gas or the like used in the processing apparatus remains on the surface of a wafer, it may cause corrosion of a wiring material on the wafer surface and deterioration in yield. To avoid such a problem, as in the FOUP, when the atmosphere replacement apparatus is provided to make a nitrogen atmosphere inside the wafer transport chamber, since the volume of the wafer transport chamber is large, a large amount of nitrogen gas is required, increasing the cost, and it takes a long time to replace nitrogen. Further, if nitrogen leaks from the EFEM, it may cause a problem of oxygen deficiency in the surrounding. Further, in recent years, an EFEM capable of connecting multiple FOUPs has been proposed in order to increase the efficiency. This increases the volume of the wafer transport chamber, and the above problem may become conspicuous.
In addition, the above problem arises similarly during transportation of a substrate other than a wafer, as long as the transportation is done in an atmosphere different from a processing or storage location.
The present invention has been made to solve efficiently the above problems. In particular, it is an object of the invention to provide an atmosphere replacement apparatus capable of replacing atmosphere on a surface of a substrate during transportation by a small amount of gas, a substrate transport apparatus, a substrate transport system, and an Equipment Front End Module (EFEM).